1. Field of the Invention
The present invention relates to a thin film magnetic head having at least an inductive magnetic transducer for recording, a method of manufacturing the same, and a magnetic recording apparatus on which the thin film magnetic head is mounted.
2. Description of the Related Art
In recent years, in association with improvement in areal density of a magnetic recording medium (for example, a hard disk), improvement in performance of a thin film magnetic head to be mounted on a magnetic recording apparatus (for example, a hard disk drive) is demanded. Known recording methods of a thin film magnetic head are, for example, a longitudinal recording method in which the orientation of a signal magnetic field is set to an in-plane direction (longitudinal direction) of a hard disk and a perpendicular recording method in which the orientation of a signal magnetic field is set to a direction orthogonal to the surface of a hard disk. At present, the longitudinal recording method is widely used. However, when a market trend accompanying improvement in surface recording density of a hard disk is considered, it is assumed that, in place of the longitudinal recording method, the perpendicular recording method will be regarded as a promising method in the future for the following reason. The perpendicular recording method has advantages such that high linear recording density can be assured and a recorded hard disk is not easily influenced by thermal fluctuations.
A thin film magnetic head of the perpendicular recording method has a thin film coil for generating a magnetic flux and a magnetic pole layer for executing recording process by emitting the magnetic flux generated by the thin film coil toward a hard disk. The magnetic pole layer has an exposed face (hereinbelow, called “magnetic pole end face”) exposed to the air bearing surface. The magnetic pole end face has, for example, a rectangular shape. In the thin film magnetic head, when current flows in the thin film coil, the magnetic flux for recording is generated in the thin film coil. When the magnetic flux is emitted from the magnetic pole layer toward a hard disk, the hard disk is magnetized by the magnetic field (perpendicular magnetic field) for recording which is generated on the basis of the magnetic flux, so that information is magnetically recorded on the hard disk. At this time, a recording pattern is determined on the basis of the trailing edge as a substantial recording part in the magnetic pole layer, that is, the edge on the trailing side of the magnetic pole end face, and information is written into the hard disk along the recording pattern. Consequently, the recording track width at the time of recording information onto a hard disk is specified on the basis of the width of the trailing edge.
To improve recording performance of the thin film magnetic head of the perpendicular recording method, or example, it is necessary to suppress the influence of a problem caused by a skew in the thin film magnetic head as much as possible. The skew is a phenomenon that the thin film magnetic head is inclined with respect to the swing of the arm of a hard disk during operation of a hard disk drive. In the case where the magnetic pole end face of the magnetic pole layer has a rectangular shape, when the thin film magnetic head skews, the recording pattern becomes more likely to be enlarged or to be distorted due to the shape. If information is recorded on a hard disk in a state where the recording pattern is enlarged or distorted, a crosstalk occurs at the time of reproducing the information, and the error rate increases, that is, the recording performance deteriorates.
Hitherto, some techniques regarding the configuration of a thin film magnetic head and a method; of manufacturing the thin film magnetic head capable of suppressing enlargement or distortion of a recording pattern due to the skew have been already proposed.
Concretely, for example, there is a known method of forming an insulating layer so as to have an inverted-trapezoid-shaped trench by using the etching technique or lift-off technique and, after that, forming the magnetic pole layer in the trench of the insulating layer in order to form a magnetic pole layer whose magnetic pole end face has an inverted-trapezoid shape in place of the rectangular shape refer to, for example, Japanese Patent Laid-open No. 2002-197613). In the case of using the etching technique in the method, after an insulating layer is formed, the insulating layer is selectively etched by using a mask, thereby forming a trench having an inverted trapezoid shape in the insulating layer. On the other hand, in the: case of using the lift-off method, a mask for liftoff is formed, an insulating layer is formed so as to cover the mask and the periphery of the mask, and the mask is lifted off, thereby forming the insulating layer having an inverted-trapezoid-shaped trench.
As the shape of the magnetic pole end face of the magnetic pole layer, except for the inverted trapezoid shape, a shape obtained by combining a rectangle rectangular region) and an inverted trapezoid (inverted-trapezoid region) is also known. Concretely, a hexagonal shape in which the width of the rectangular region and the maximum width of the inverted-trapezoid region are equal to each other (refer to, for example, Japanese Patent Laid-open No. 2003-242607), an almost-T-shape in which the width of the rectangular region is wider than the maximum width of the inverted-trapezoid region (refer to, for example, Japanese Patent Laid-open No. 2003-242608), and the like are known. In the case of forming the magnetic pole layer including the magnetic pole end face having the hexagonal shape or almost-T-shape, for example, a lower layer portion corresponding to the inverted-trapezoid region is formed by using a method of forming the magnetic pole layer including the magnetic pole end face having the inverted-trapezoid shape and, after that, an upper layer portion corresponding to the rectangular region is formed on the lower layer portion, thereby forming the magnetic pole layer by the process of two steps. For example, in the case of forming the magnetic pole layer by using a polishing process to planarize the trailing edge, the magnetic pole layer having the magnetic pole end face of this kind has an advantage from the viewpoint of precision of formation of the magnetic pole layer. Specifically, in the case of forming the magnetic pole layer including the magnetic pole end face of the shape obtained by combing the rectangle and trapezoid by using the polishing process, different from the case of forming the magnetic pole layer having the magnetic pole end face of the inverted trapezoid shape by using the polishing process, as long as the polishing amount of the magnetic pole layer is set to be within the range of the height of the rectangular region, the width of the trailing edge is always determined on the basis of the width of the rectangular region. Consequently, variations in the width of the trailing edge caused by variations in the polishing amount of the magnetic pole layer are suppressed.
To spread the thin film magnetic head of the perpendicular recording method, it is important to establish a manufacturing technique capable of manufacturing, for example, a thin film magnetic head of high performance with high precision. With respect to this point, the conventional method of manufacturing a th film magnetic head capable of forming a magnetic pole layer having a magnetic pole end face of the shape obtained by combining the rectangle and inverted trapezoid is useful as the manufacturing technique for manufacturing a high-performance thin film magnetic head with high precision. However, when mass productivity and manufacture easiness are considered in addition to the performance and manufacture precision as described above to spread thin film magnetic heads, since the lower layer portion corresponding to the inverted trapezoid region and the upper layer portion corresponding to the rectangular region are formed separately in manufacturing a thin film magnetic head, that is, the magnetic pole layer is formed by the process of two steps, the process of forming the magnetic pole layer is complicated and the number of processes required to form the magnetic pole layer is large. Consequently, there is still room for improvement in the conventional method of manufacturing a thin film magnetic head from the viewpoint of forming the magnetic pole layer as easily as possible.